Where did Jesus first meet Simon Peter and Andrew?

Matthew 4:18-19 and John 1:42-43

There is no contradiction here at all. The chronology of events becomes evident when viewing the grid below. In John 1:35ff, John the Baptist was with his disciples. He tells them that Jesus is the "Lamb of God" (v. 36) and they stay with Jesus a while (v. 37). In John 1:40-42, Andrew goes and gets Simon-Peter and they follow Jesus. Why? Because Andrew had spent time with Jesus and told Simon that Jesus was the Messiah (v. 41). Later, in Matt. 4:18, Jesus was walking by the Sea of Galilee and He sees Simon-Peter and Andrew as they were fishing. He had not asked them to follow Him until this point in verse 4:19. They do (4:20). There is no contradiction.

Event	Matthew 4:18-20	John 1:35-42
John Baptist sees Jesus		35 Again the next day John was standing with two of his disciples,
"Lamb of God"		36 and he looked at Jesus as He walked, and said, "Behold, the Lamb of God!"
John tells his disciples to come see the lamb.		39 He said to them, "Come, and you will see." So they came and saw where He was staying; and they stayed with Him that day, for it was about the tenth hour.
Andrew followed Jesus.		40 One of the two who heard John speak and followed Him, was Andrew, Simon Peter's brother.
First, Andrew got Simon/Peter		41 He found first his own brother Simon and said to him, "We have found the Messiah " (which translated means Christ ).
Andrew brings Simon to Jesus		42 He brought him to Jesus. Jesus looked at him and said, "You are Simon the son of John; you shall be called Cephas " (which is translated Peter ).
Jesus by sea of Galilee, sees Andrew	18 Now as Jesus was walking by the Sea of Galilee, He saw two brothers, Simon who was called Peter, and Andrew his brother, casting a net into the sea; for they were fishermen.
Jesus says to Andrew and Simon, "Follow Me..."	19 And He said to them, "Follow Me, and I will make you fishers of men." 4:20 Immediately they left their nets and followed Him.