McGuane came off the bench in the 76th minute as Barcelona overcame Espanyol 4-2 on penalties after a goalless draw in the Supercopa de Catalunya.
The England youth international arrived from Premier League side Arsenal in January, joining Barca's B team after signing a contract which includes a release clause of €25million.
"It was a massive experience for me and my family. Words can't really describe how it felt walking out there. But it felt really good," McGuane said. "When the coach told me I'm coming on I thought just be calm and play my game and show what I can do."
Former England international Lineker swapped Everton for Barcelona in 1986.
Lineker won the Copa del Rey and European Cup Winners' Cup before leaving Barcelona in 1989, having scored more than 50 goals in all competitions.
"A lot of people told me when I signed that Gary Lineker was the last English person to play for FC Barcelona. So to know that I'm next, that's some achievement," McGuane said. "I need to carry on pushing on with the B team and get as many games as possible. And if get any opportunities to go over to the first team, I've just got to show the boss what I can do."
Ousmane Dembele, Jasper Cillessen and Yerry Mina were among the first-team players to feature, while Paco Alcacer and Denis Suarez also played.
Suarez sustained a groin injury in the clash and will undergo tests to determine the full extent of the problem.
"The game went through many phases and had a lot of changes," said head coach Ernesto Valverde. "We started well but there were times when our game fell off a little. But we ended with almost only B team players on the pitch and it was a good chance to see them in action."