George Brett extended his hitting streak to 13 games and Hal McRae drove in two runs yesterday to lead the Royals to a 7-1 victory over the Toronto Blue Jays in Kansas City.

Brett reached base the first three times he went to the plate, on a double, a walk and a single. When he finally made an out in the sixth inning, it was a 400-foot fly ball to dead center field. Overall, he has a 19-game hitting streak--the final six games of 1982 and the first 13 games of 1983.

Brett raised his average to .471.

"It goes back to the theory I developed in 1980," said Brett of his good start. "The longer you wait, the better you see it (pitch); the better you see it, the harder you hit it; the harder you hit it, the higher your average will be.

"That's the way it was in 1980 and that's the way it is now. The difference is that I was that way for three months in 1980; I've only been like that for 13 games this year."

McRae gave Kansas a 1-0 lead in the third with a bases-loaded ground ball that scored Willie Wilson, drove in a run with a single during the fifth-inning rally, which included five walks.