McDonald produced a solid performance for Australia in their 2-1 friendly win over Wales in Cardiff during the week before playing alongside the on-fire Marvin Emnes in Boro's 1-0 away win at Leeds United in the Championship on Saturday.
Mowbray praised the 27-year old for his ability to now help out his fellow striker which adds another string to his bow.
"I watched the match and it was a very, very good performance from Scott McDonald for his country," Mowbray said.
"I thought he was outstanding alongside Tim Cahill. He'll hopefully come back from that game feeling good about himself.
"The technical side of his game is getting much, much better. He didn't give the ball away once in 90 minutes, his movement was very intelligent and he threatened the goal.
"I'm delighted he's taken those attributes on board and that's made him a better all-round footballer, not just someone who wants to score goals. He covers a lot of ground and works extremely hard."
And Mowbray was not worried about McDonald's barren start to the domestic season with the Teessiders.
"As we stand here now I'm pretty sure Scott McDonald will be our top scorer as long as he stays fit," he added.
"That's the nature of the boy - he's desperate to score goals every game. He's been involved in a lot of the good stuff we've done this season, if not scoring goals then creating them."