McKinney, an outfielder out of Texas' Plano West High School who had committed to Texas Christian University, will receive a $1.8 million bonus, which is slightly less than the assigned value of $1,893,500 for the No. 24 overall pick.
The 18-year-old left-handed hitter finished his senior season batting .394 (39-for-99) with six home runs and 32 RBIs. He also drew 36 walks in 130 plate appearances for a .585 on-base percentage and struck out only six times.
McKinney was the second high school player selected in the first round by the A's in as many years. Before picking shortstop Addison Russell out of Florida's Pace High School last year, Oakland had not taken a prep player with its first selection since Jeremy Bonderman in 2001.
McKinney can play all over the outfield and has plenty of experience at first base, but the A's plan to let him begin his professional career as a center fielder, his natural spot.
"You can say his tools are more average than plus, but he makes up for that in the outfield with instincts and jumps and reads," said A's scouting director Eric Kubota last week. "He's a very instinctual player, and that's why we think he has a chance to play center field. It's hard not to like the way this kid plays. He plays the game with intensity and energy. He's just the kind of guy that people will enjoy watching."
It's not yet known where McKinney will report to begin his career, though it's likely the A's start him in the Arizona Rookie League.
Following McKinney, the A's plucked Oklahoma left-handed pitcher Dillon Overton and Virginia Tech shortstop Chad Pinder with their second-round selections, before picking Oregon first baseman Ryon Healy 100th overall. Kohler was their next pick at No. 106.
Kohler was 11-1 with a 2.24 ERA in 12 starts as a senior for Los Osos (Calif.) High School, striking out 113 batters in 72 innings while holding the opposition to a .201 clip.
Covey, tabbed by the A's with the 131st-overall pick, went 5-4 with a 5.05 ERA in 18 games, including 16 starts, for the University of San Diego. He was a first-round selection of the Brewers in 2010 but, after being diagnosed with Type 1 diabetes, opted to go to college to learn how to pitch with the disease.
The A's also inked the following players on Tuesday: OF Tyler Marincov (8th round, North Florida); LHP Matt Stalcup (9th, Pittsburg State), LHP Jerad Grundy (10th, Kentucky); RHP Louis Trivino (11th, Slippery Rock); RHP Dakota Freese (12th, Des Moines Area CC); OF Justin Higley (13th, Cal State Sacramento); RHP Junior Mendez (16th, Southern New Hampshire); OF Jaycob Brugman (17th, Brigham Young); RHP Samuel Bragg (18th, Georgia Perimeter College); CF Scott Masik (21st, Cal State Los Angeles); RHP Trevor Bayless (22nd, San Diego); C Josh Miller (23rd, South Carolina-Aiken); RHP Kevin Johnson (24th, Illinois); RHP Jon Massad (25th, Southern New Hampshire); C Kyle Wheeler (26th, Belhaven), 1B Ryan Huck (27th, Western Kentucky); 2B Joseph Bennie (28th, East Stroudsburg); RHP Blake McMullen (29th, Science & Arts of Oklahoma); OF Benjamin McQuown (30th, Campbell); RHP A.J. Burke (31st, Western Oregon State), RHP Dominique Vattuone (32nd, UNC-Greensboro); RHP Joseph Michaud (33rd, Bryant); 3B Austin Kubala (34th, Arlington County Day School).
That leaves Oakland with only 14 unsigned players from the 2013 First-Year Player Draft.